In a typical exposure apparatus of this type, the light, which is radiated from a light source, forms, via a fly's eye lens as an optical integrator, a secondary light source as a substantial surface light source composed of a large number of light sources (in general, a predetermined light intensity distribution on an illumination pupil). In the following description, the light intensity distribution, which is provided on the illumination pupil, is referred to as “pupil intensity distribution”. Further, the illumination pupil is defined as the position which makes the illumination objective surface or illumination objective plane (mask or wafer in the case of the exposure apparatus) the Fourier transform plane of the illumination pupil by the aid of the action of the optical system disposed between the illumination pupil and the illumination objective surface (plane).
The light, which comes from the secondary light source, is collected by a condenser optical system, and then illuminates a mask, on which a predetermined pattern is formed, in a superimposed (overlaid) manner. The light, which is transmitted through the mask, forms an image on a wafer via a projection optical system, and the mask pattern is projected and exposed (transferred) onto the wafer. The pattern, which is formed on the mask, is fine and minute. In order to correctly transfer the fine pattern onto the wafer, it is indispensable to obtain a uniform illuminance distribution on the wafer.
Conventionally, it has been suggested a technique in which an annular (circular zonal) or multi-pole-shaped secondary light source (pupil intensity distribution) is formed on an illumination pupil defined on a back focal plane of a fly's eye lens or in the vicinity thereof by the action of an aperture diaphragm which is equipped with a wave plate (a wavelength plate) and which is arranged just downstream from the fly's eye lens, and the setting is made such that the light beam (luminous flux), which passes through the secondary light source, is in a linear polarization state in which the circumferential direction is the polarization direction (hereinafter abbreviated and referred to as “circumferential direction (azimuthal direction) polarization state”) (see, for example, Japanese Patent Publication No. 3246615).